Technology Field
The invention of this disclosure relates to a pressure sensing systems and, more particularly, to a pressure sensing systems having increased pressure sensitivity.
Description of the Related Art
An electric device is often equipped with an input interface having a pressure sensing function, as a touch pad, for sensing touch pressure (e.g., finger touch pressure). Thus, when the touch pad senses a finger touch, the electric device may execute a corresponding event based on the position or the pressure of the finger touch.
FIG. 1 is an exploded perspective view of a conventional touch pad, as is known in the prior art. As illustrated, touch pad 500 has a touching layer 510, a flexible layer 520, and a circuit layer 530. The touching layer 510 is located above both the flexible layer 520 and the circuit layer 530, and is designed for bearing a pressure. The flexible layer 520 is located between the touching layer 510 and the circuit layer 530 and separates the touching layer 510 from the circuit layer 530 to prevent shorting. The circuit layer 530 is configured to transform a finger touch pressure to an electrical signal and to transmit the electrical signal to a processor of the electric device to allow the electric device to execute the corresponding event. When the touching layer 510 is subjected to the pressure, the touching layer 510 is deflected downward and thus the pressure is transferred to the flexible layer 520. At that time, both the touching layer 510 and the flexible layer 520 become thinner at the point of contact due to the contact pressure. The circuit layer 530 may change the output resistance after sensing the variation in thickness of the touching layer 510 and the flexible layer 520. The processor can calculate the variable of the output resistance to obtain the pressure value.
However, the flexible layer has elasticity. When the touching layer 510 and the flexible layer 520 are subjected to the pressure, the elasticity of the flexible layer may offset a part of the pressure. Additionally, the recovery speed of the flexible layer after pressed may vary with the pressure and the time. Accordingly, the conventional touch pad suffers from accuracy problems.